Pyrimisulfan is a highly effective acetolactate synthase (ALS) inhibitor and a broad-spectrum herbicide. It selectively inhibits the acetolactate synthase in plants and is used for controlling a variety of paddy field weeds both pre-emergence and post-emergence, including annual grasses, sedges, broadleaf weeds, and sulfonylurea-resistant biotypes. Pyrimisulfan offers long residual activity and excellent safety for rice crops, and it is suitable for research related to paddy field herbicides.